We propose a model for data authentication which takes into account the behavior of the clients who perform queries. Our model reduces the size of the authenticated proof when the frequency of the query corresponding to a given data is higher. Existing models implicitly assume the frequency distribution of queries to be uniform, but in reality, this distribution generally follows Zipf’s law. Therefore, our model better reflects reality and the communication cost between clients and the server provider is reduced allowing the server to save bandwith. When the frequency distribution follows Zipf’s law, we obtain a gain of at least 20% on the average proof size compared to existing schemes.